Virtualization Functions (NFVI, VNF)

A network function (NF) is a function that is performed by a physical appliance like a router, switch, firewall, load balancer, IDS, WAN optimizer, etc. Most vendors have proprietary solutions in which hardware and software are tightly coupled. Cisco is a good example. They sell their routers and switches as appliances. You need the hardware and software. You cannot run Cisco IOS (officially) without the hardware and you can’t run anything else besides Cisco IOS on a router or switch.

In this lesson, you will learn about virtual network functions and the ETSI NFV architectural framework.

Virtual Network Function (VNF)

Nowadays, we can also use virtual solutions. A virtual network function (VNF) is the virtual version of a hardware device’s network function. VNFs are available as virtual machines or containers.

Here are examples of Cisco VNFs:

  • vEdge Cloud
  • CSR1000v
  • ASAV
  • Cloud Services Platform (CSP) 2100
  • XRv 9000
  • Firepower NGFWv
  • Web Security Virtual Appliance (WSAv)
  • Email Security Virtual Appliance (ESAv)
  • Advanced Malware Protection Virtual (AMPv)

The advantages of VNFs are similar to server virtualization and cloud computing. We have a shorter time to market (TTM) because, without the hardware requirement, we can quickly launch a new network function as a virtual machine or container.

We can scale up or down, in or out, on-demand. Since we don’t need physical appliances, we require less physical space and less power consumption. This results in a reduced operator capital expenditure (CAPEX) and reduced operational expenditure (OPEX).

ETSI NFV Architectural Framework

The European Telecommunications Standards Institute (ETSI) created the Network Functions Virtualization (NFV) framework which describes standards to decouple network functions from proprietary hardware appliances and instead, run them in software on standard hardware.

Vendors offer VNFs and service providers choose the VNFs that they need. If we want to run VNFs from different vendors on a single open platform, we need a standard that describes how to manage, monitor, and configure our VNFs.

The framework also describes how to manage and orchestrate VNFs. Here is a picture of the framework:

Etsi Nfv Framework

There are four components:

  • Virtualized Network Functions (VNFs)
  • Network Functions Virtualization Infrastructure (NFVI)
  • NFV Management and Orchestration (MANO)
  • Operations and Billing Support System (OSS/BSS)

Let’s walk through all of these components.

NFV Infrastructure (NFVI)

NFV infrastructure (NFVI) is all the hardware and software we need to create a platform where we can run VNFs on. Many VNFs are available as virtual machines, so this is where we find our physical servers, storage, networking, and the virtualization layer (hypervisors).

Virtualized Network Functions (VNFs)

This component is where we find our VNFs. The Element Manager (EM) is responsible for network management of one or more VNFs. The EM can also be a VNF.

NFV Management and Orchestration (MANO)

The NFV Management and Orchestration (MANO) component has three items:

  • NFV Orchestrator (NFVO): the orchestrator launches, maintains, and scales VNFs. The orchestrator also validates and authorizes resource requests from the NFVI component.
  • VNF Manager (VNFM): the VNFM performs life-cycle management (launch, maintain, and teardown) of VNFs.
  • Virtualized Infrastructure Manager (VIM): the VIM manages and controls the hardware and virtualization resources in the NFVI. It collects performance metrics, fault information, and also performs life-cycle management of all NFVI resources.

The VIM is also responsible for VNF service chaining. Server chaining means we chain multiple VNFs together to create a service or solution. Here is an example:

Cisco Csr1000v Asav Service

The CSR1000v router and ASAv are two VNFs we chain together to create a single solution. We might use the router for DMVPN and the ASAv for our firewall rules.

Operations and Billing Support System (OSS/BSS)

The Operational and Billing Support System (OSS/BSS) component has the Operations Support Systems (OSS) and Billing Support Systems (BSS). The OSS supports management functions like network inventory, management, and configuration. The BSS deals with customer management and includes systems for taking orders, payments, etc.

The acronyms OSS and BSS are often used interchangeably or abbreviated as OSS/BSS.

Cisco NFVI

Cisco has an NFVI solution called Cisco NFVI  and is based on the ETSI NFV framework. NFVI uses a combination of Cisco products and Red Hat (RHOL) OpenStack. Here is an overview:

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Forum Replies

  1. Hello Umesh

    The NFVI as a framework has several components. These components can be separated into two categories: hardware and virtual. Among the hardware components are the Nexus series devices. Nexus devices essentially provide the physical connection to the virtualized NFVI environment. Looking at the diagram below, the nexus switches would fall under the “Hardware Network” component at the bottom right.

    This might sound philosophical, but I b... Continue reading in our forum

  2. Hello Laz,
    Thanks for clarification.

  3. Hello Hussein

    I have been unable to find any info about this specific statement, and the strange thing is that I cannot find anyone stating anything about it in the Cisco forums either. However, my feeling is that it has to do with VM orchestration, dealing with Layer 4 to Layer 7 services, similar to what is contained in the following Cisco documentation.

    ... Continue reading in our forum

  4. Hi Hussein,

    I also did some research, trying to find a connection with either NFVI, VNF, or cloud. To be honest, I have no idea. NFVI/VNFs are about L2-L7, same with cloud. I can’t think of anything. I’d say that virtualization starts at L3 (routers) and NFVI/VNF goes up to L7.

    Nothing I can think of that sits in between L4-L6.


  5. Thank you both @ReneMolenaar & @lagapides

    I think Cisco not mean OSI layers model in this sentence instead they are meaning virtualization layers, also when I make a little search about that I found something interesting and it’s very related to virtualization function which is what this post about, in short virtualization layer mean at which level we can mange physical hardware resources for example host (Hypervisor) level, guest OS level, or program level (High-level language virtual machines), and so on, I revert this info from this wiki :-

    ... Continue reading in our forum

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